1. Field of the Invention
The present invention relates to a flat display device, and more particularly, to a spacer supporting structure for a flat display device adapted to maintain a gap between two panels of the flat display device and a method of supporting spacers.
2. Description of the Related Art
Typical important applications of display devices include monitors for personal computers and television screens. The display devices include Cathode Ray Tubes (CRTs), which use the emission of heated electrons at a high speed, and flat display devices, which have rapidly developed in recent years, such as Liquid Crystal Displays (LCDs), Plasma Display Panels (PDPs), and Field Emission Displays (FEDs).
The flat display devices, such as FEDs, have electrons emitted in a vacuum space and light generated by a fluorescent material excited by the emitted electrons. The flat display devices include a front panel, a rear panel, and spacers between the front panel and the rear panel. The FED includes a stacked structure including an anode and a fluorescent layer arranged on the front panel, and an electron emitter, such as a micro tip or a Carbon NanoTube (CNT), a cathode and a gate electrode for controlling electron emission arranged on the rear panel.
The space between the front panel and the rear panel is maintained in a vacuum state. Therefore, the front panel and the rear panel are apt to deform due to atmospheric pressure or other external pressure. In this case, components between the two panels can be damaged, especially when a gap between the front panel and the rear panel becomes uneven due to a deformation, in which case the electron emission and the control of the emission may be impossible.
Therefore, the gap between the front panel and the rear panel of a flat display device such as a FED should remain fixed. For this purpose, spacers are interposed between the two panels. The spacers should be located at positions that do not interfere with the display of an image.
A cross-shaped spacer and a bar-shaped spacer are widely used in flat display devices.
The cross-shaped spacer is manufactured piece by piece by etching or injection molding. In order to maintain the gap between the front panel and the rear panel, the cross-shaped spacer is required to dispose about one˜five pieces per square centimeter. Generally, the cross-shaped spacer is mounted by an adhesive on the rear panel. More specifically, a small amount of the adhesive is coated on the rear panel or on the spacer and then the spacer is attached to the rear panel.
The cross-shaped spacer can be attached to a correct location on the rear panel since it is mounted piece by piece, and almost no deformation is observed after sealing at a high temperature during the manufacturing process of flat display devices.
However, mounting the numerous cross-shaped spacers on the rear panel of a large flat display device can take a long time. Also, the rear panel can be contaminated by the adhesive used to attach the cross-shaped spacers, and the contamination of the rear panel can degrade the image quality of the flat display device.
A bar-shaped spacer is manufactured by cutting a ceramic sheet or a glass sheet into a bar shape with desired dimensions. The bar-shaped spacer is mounted by attaching both ends of the bar-shaped spacer to a separately prepared fixture using an adhesive.
The bar-shaped spacer is easily manufactured and requires a short installation time. Also, there is little possibility of contamination of an active region of the panel since the adhesive is only applied to the ends of the bar-shaped spacer.
However, the bar-shaped spacer is not well suited to a high temperature sealing process since it only has support along one dimension. More specifically, the panel and the bar-shaped spacer expand and contract by different amounts during and after the high temperature sealing process because they have different thermal expansion coefficients. Therefore, the bar-shaped spacer can bend. If so, the bar-shaped spacer may not remain in the correct position, resulting in misalignment of the bar-shaped spacers, cathodes, and anodes.
A protrusion of a contact portion between a spacer and the rear panel into a pixel region can occur due to a misalignment of a bar-shaped spacer after a high temperature sealing process. When there is a misalignment of a bar-shaped spacer, the spacer may cover a pixel or interact with an electron beam between anodes and cathodes, which can cause a bright spot due to an electron charging effect, or can cause arcing due to a partial distortion of an electric field.
To minimize an alignment error of the spacers, cathodes and anodes caused by the thermal expansion coefficient differences, only one end of the spacers is fixed. In this case, the problems associated with the thermal expansion coefficient differences are reduced to some degree since the thermal expansion and contraction of the bar-shaped spacer is relatively free. However, since the spacers are fixed only at one end, the alignment can easily be distorted by the flow of an inert gas injected between the two panels to prevent an oxidation of an electron emitter at a high temperature.